In our earlier patent application published as WO 99/29262 there was disclosed a stent graft including at least one fenestration to enable an extension leg graft to be extended from a main stent graft in an internal lumen through the fenestration to have the extension leg or arm graft extend into a branch vessel of the lumen. Such a situation may exist in the aorta with renal arteries extending from the aorta. When there is an aneurysm in this region which includes the junction of the aorta with the renal arteries then it is desirable to not only have a main graft which spans the aneurysm but also extension legs or arms which extend from the main graft into the renal or other arteries.
A simple fenestration does not necessarily give a fully reliable support and sealing surface for the extension leg graft and it is the object of this invention to improve the ability for support and sealing of an extension leg or arm grafts into a main graft.